The invention relates generally to a leak-free, container having a piston device that is directed to accomplish a plurality of preferred goals simultaneously. Specifically, the present invention piston device is directed to: elimination or very significant reduction of air inside the containment area of liquids of different viscosity, such us water, milk, oils, creams, pureed foods, chocolate mousse, yogurts, and the like to keep the contents air-free to prevent spoiling. The piston moves towards a suction force to deliver air-free contents. For example, when this airless container is used as a baby bottle, it very significantly reduces gas-creating air during feeding or drinking; and the accomplishment of the foregoing with minimal, user-friendly components. Preferred embodiments also provide the following additional benefits: 100% air free to help prevent gas and gas associated effects from air ingestion; allows user to expel air by pushing the piston from the bottom up; helps retard oxidation to retain nutrients that are lost when the bottle's contents comes in contact with air; and works on suction as opposed to gravity, so the user can feed in any angle. Further, there are included herein unique component features and materials of construction that create leak proof connections and functionality of the present invention devices. The container and piston device work on suction as opposed to gravity, so the user can dispense by a pump or spray or directly suck to ingest the contents in any angle.